Coating compositions

ABSTRACT

A coating composition capable of being crosslinked on a substrate to which it is applied which contains an acidic filmforming material containing at least two carboxyl groups and a phenolic material containing at least two 47 groups -CH2.NR1R2 substituted in positions ortho and/or para to one or more phenolic hydroxy groups, R1 and R2 being alkyl or substituted alkyl groups.

United States Patent Palluel June 27, 1972 [54] COATING COMPOSITIONS[56] References Cited [72] Inventor: Auguste Louis Luciene Palluel,Windsor, UNITED STATES PATENTS England 2,890,095 6/1959 Meister et al..260/51.'5 [73] Assigneez Imperial Chemical Industries Limited, 3 230162 1/1966 Gilchrist Englanfi 3,351,575 11/1967 Gilchrist ..260/844 22Filed; 9, 19 9 R25,213 7/1962 Runk et a]. ..260/20 [211 875,0 PrimaryExaminer-Donald E. Czaja Assistant ExaminerWilliam E. Parker RelatedApphcatlon Dam Attorney-Cushman, Darby & Cushman [63] Continuation ofSer. No. 624,128, March 20, 1967,

abandoned. [57] ABSTRACT 30 F P D ta A coating composition capable ofbeing crosslinked on a sub- 1 orelgn App [ca Duty a strate to which itis applied which contains an acidic film- March 25, 1966 Great Britain13,323/66 forming material containi g at least two carboxyl groups and aphenolic material containing at least two 47 groups -CH .NR [1.8- CI...,R substituted in positions onho and/or para to one o more 260/842:260/844 phenolic hydroxy groups, R and R being alkyl or substituted [5]]Int. Cl ..C08g 5/20 alky] groups [58] ..260/19, 842, 844, 293,459

13 Claims, N0 Drawings COATING COMPOSITIONS This application is acontinuation of Ser. No. 624,128 filed Mar. 20, 1967, now abandoned.

BACKGROUND OF INVENTION This invention relates to crosslinkable coatingcompositions which contain an acidic film-forming material and aphenolic material.

It is well established that certain film-forming materials may bemodified by crosslinking chemical groups within the material so'thatthey become, for example, insoluble in common solvents and resistant tochemical attack. When these materials are employed in coatingcompositions it is convenient to apply them to a substrate as a solutionor as a dispersion in a suitable liquid medium and subsequently modifythem on the substrateby crosslinking. The modification may be achievedfor example, by the direct crosslinking of groups in the material orthrough a crosslinking agent which contains chemical groups reactivetowards certain chemical groups in the film-forming material.

SUMMARY We have now found that certain acidic film-forming materials maybe crosslinked by certain phenolic materials and that a combination ofthese two types of material is suitable in a crosslinkable coatingcomposition.

DESCRIPTION OF PREFERRED EMBODIMENTS According to the present inventionwe provide a coating composition which comprises an acidic film-formingmaterial containing at least two carboxyl groups per molecule and aphenolic material containing at least two groups CI-I .NR,R per moleculesubstituted in positions ortho and/or para to one or more phenolichydroxy groups, wherein R, and R are alkyl or substituted alkyl groups,the same or different.

The coating compositions of this invention may be applied byconventional processes to a substrate from any suitable aqueous ornon-aqueous medium in which the components can be dissolved ordispersed. The acidic film-forming material may be crosslinked during orafter application, for example, by heating.

The compositions are particularly suitable for application from anaqueous medium since the carboxyl groups of the film-forming materialenable it to be dissolved or dispersed in such medium, normally in thepresence of a base.

Suitable acidic filmforming materials include:

1. Materials containing a maleinised drying oil fatty acid ester such asthe maleinised drying oils, for example maleinised dehydrated castoroil, maleinised soya bean oil, maleinised linseed oil, and fumarisedtung oil; the products obtained by reacting maleinised drying oil fattyacids with suitable hydroxyl-containing bodies such as polyols in whichterm we include the epoxy resins; and the products obtained by reactingmaleic anhydride with esterified drying oil fatty acids.

2. Additioncopolymers in which one of the polymerized comonomerscontains a carboxyl group, for example a copolymer of an alkyl acrylateand/or an alkyl methacrylate and acrylic acid in which there are atleast two carboxyl groups per molecule. Suitable carboxyl-containingco-monomers include acrylic acid, methacrylic acid and maleic anhydride,and suitable monomers polymerizable therewith include, for example,methyl methacrylate, ethyl acrylate, butyl methacrylate, styrene andvinyl toluene.

3. Alkyd resins which contain free carboxyl groups, for example, thoseof high acid value based on trimellitic anhydride, a suitable polyolsuch as pentaerythritol and optionally drying oil fatty acids and otheracids.

It is understood for the purpose of this invention that a carboxylicacid anhydride group is equivalent to two carboxylic acid groups.

When the coating composition comprises an aqueous medium, the acid valueof the acidic film-forming material is preferably greater than 30mg.KOI-I/gm.

Suitable bases which may be employed to aid dissolution or dispersion ofthe acidic film-forming material in an aqueous medium include ammoniaand water-soluble organic amines such as diethylamine, triethylamine,diethanolamine and triethanolamine and in certain applications inorganicbases such as sodium and potassium hydroxide.

The phenolic material with which the acidic film-forming material iscombined in the present coating compositions contains at least twogroups of structure -CH .NR,R per molecule which are substituted in oneor more aromatic rings and which are activated by a phenolic hydroxygroup by virtue of being in an ortho and/or para position to such agroup.

The groups R, and R are alkyl or substituted alkyl groups, the same ordifferent, and in general R, and R each contain from one to 18 carbonatoms. Preferably R, and R each contain from one to six carbon atoms butthe nature of the alkyl group and substituents therein, will bedetermined to a large extent by the nature of the medium from which thecoating composition is applied. For example when R, and R are loweralkyl groups the phenolic material will be more soluble in polar media,e.g. an aqueous medium, and when R, and R are higher alkyl groups thephenolic material will be more soluble in non-polar media.

Suitable substituents in the alkyl groups include hydroxy] groups.

The phenolic material may contain one or more phenolic residues permolecule and there may be one or more phenolic hydroxy groups in eachsuch residue, for example the phenolic residue may be derived fromphenol or resorcinol.

Suitable phenolic materials include for example those obtained byintroducing at least two CI-I .NR,R groups into the positions orthoand/or para to the hydroxy group of phenols such as phenol, resorcinol,p-tertiary butyl phenol, p-

octyl phenol, p-phenyl phenol and phenols which .contain more than onephenolic residue, for example 2,2'-diphenylol propane.

Particularly preferred phenolic materials are the 2,2- diphenylolpropanes and derivatives thereof having at least two substituents CI-I.NR,R in positions ortho and/or para to a phenolic hydroxy group.

The number and chemical nature of nuclear substituents other than theCI-I .NR,R groups on the parent phenol may be selected, according towell known principles, in order to improve compatibility with the acidicfilm-forming material or solubility in the selected coating compositionmedium; provided that at least two sites remain available on thephenolic residue or residues ortho or para to a phenolic hydroxy, for atleast two of the groups CI-l .NR,R Alkyl, aryl and aralkyl substituentson the phenol will improve its compatibility with oil modifiedfilm-formers and its solubility in hydrocarbon solvents whilst carboxyl,carboxy alkyl and polyethenoxy groups will improve solubility ordispersibility in an aqueous medium.

In order to improve solubility or dispersibility in an aqueous mediumhydrophilic groups may also be present as substituents in the alkylgroups R, R of the groups CI-I .NR,R of the phenolic material and thesegroups may be varied when introduced for example, by the method hereindescribed for preparing the phenolic materials in which there isemployed a secondary amine NI-IR,R Examples of suitable hydrophilicgroups include hydroxy and carboxyl groups. I'Iydroxy groups, forexample, may be introduced by using as the secondary amine, adihydroxyalkylamine such as diethanolamine. In general there is employedfrom 0.5 to 50% by weight of the phenolic material based on the totalweight of that material and the acidic film-forming material.

The phenolic material is convenientlyprepared for example, by reacting aphenol which may comprise one or more phenolic residues withformaldehyde and asecondary amine, NHR,R wherein R, and R are alkyl orsubstituted alkyl groups the same or different, under theconditionsemployedv in the known Mannich reaction. In general it isnecessary to for example a lower alcohol or anether alcohol. Acidic orbasic catalysts may be added to the reaction mixture, but more usuallythe modifying secondary amine provides suitable basic conditions for thereaction. The temperature of reaction is that usually employed for theformation of phenol-formaldehyde condensates; that is from roomtemperature to about Typical parent phenols which maybe-employed in thepreparation of the phenolic material by this method include for examplethose already mentioned above. The choice of the phenol will dependparticularly upon the nature of the acidic film-forming material whichthe phenolic material is required to crosslink and upon the medium fromwhich the composition is to be applied.

in the secondary amine NHR,R the groups R and R are alkyl or substitutedalkyl groups, particular groups .being chosen in general to facilitatethe use of the phenolic material in various media. In general the alkylgroups R and R may each contain from one to 18 carbon atoms, butpreferably from one to six carbon atoms. Typical amines which aresuitable .include dimethylamine, diethylamine, diethanolamine,dicyclohexylamine and morpholine.

The present coating compositions may be applied to a variety ofsubstrates such as metal, wood or hardboard, by a variety of processesfrom an aqueous or non-aqueous medium.

In addition to the acidic film-forming material and the phenolicmaterial there may be present in the composition other acidic ornon-acidic film-forming materials and other materials conventionallyused in coating compositions for example pigments, fillers, extenders,surfactants and thickeners.

When applied from an aqueous medium the phenolic material and the acidicfilm-forming material are preferably water-soluble or water-dispersibleand suitable methods of application from an aqueous medium include forexample, brushing, spraying, dipping, or electrodeposition. Afterapplication of the composition to a substrate the acidic film-formingmaterial is normally cross-linked by the phenolic material. Crosslinkingis usually effected by stoving at a suitable temperature, for example intherange 120200 C, depending on the nature of the substrate and thematerial to be crosslinked.

It is preferred that there is present in the aqueous medium a watermiscible organic liquid for example the monobutyl ether of ethyleneglycol and other monoaklyl ethers of ethylene glycol, and butanol.

The present compositions are particularly suitable for application to anarticle by a process of electrodeposition in which an electric currentis passed through an aqueous medium containing a solution and/or adispersion of a composition according to the invention in the presenceof a base. between the article and another electrode immersed in themedium.

In such a process the phenolic material may advantageously contain atleast one carboxyl group to assist in its deposition upon the article ina required proportion relative to that of the acidic film-formingmaterial. Such a carboxyl group may be introduced by a procedureanalogous with that described above, for example by condensing an aminocarboxylic acid or a derivative thereof in the presence of formaldehydewith at least one phenolic residue to effect substitution in a positionortho and/or para to a phenolic hydroxy group.

The phenolic materials may be combined with a wide range of acidicfilm-forming materials for application by the electrodeposition processwhen these materials are soluble and/or dispersible in water or anaqueous medium. Typical acidic resins which are soluble or dispersiblein water in the presence of a base and which are suitable inelectrodeposition are those already referred to above. Suitable baseswhich may be used to solubilize or disperse the acidic film-formingmaterial for electrodeposition include ammonia and the water-solubleorganic amines and inorganic bases such as sodium and potassiumhydroxide. It is preferred in the electrodeposition process to employfrom 0.5 to 40% by weight of the phenolic material based on the totalweight of agent and film-forming resin.

The invention is illustrated by the following Examples in 3 which partsand precentages are by weight unless otherwise stated.

1 EXAMPLE 1 1 mole proportion of diphenylol propane was dissolved withwarming in 4 mole proportions of diethanolamine (88% solution in water);to this solution were added 4 mole proportions of formaldehyde (37% inwater) and reaction allowed to proceed at 90 C. until no furtherincrease in viscosity was observed. The product could be diluted withwater. I

An aqueous solution of the phenolic product was blended with thefollowing film-forming materials in a solids ratiophenolic product tofilm-forming material of 40 to 60 by weight. (a) A solution of amaleinised bodied linseed oil (in which maleic anhydride had beenreacted with bodied linseed oil in a molar ratio of 2 to l neutralizedwith ammonia; (b) a solution of fumarised tung oil (in which fumaricacid had been initially reacted with tung oil in a molar ratio of 2 to lneutralized with ammonia.

Typical metal paint primers were made from these blends pigmented withbarytes and red iron oxide in the respective weight ratio of 3 to l thepigment to binder volume ratio being 3:7, and the resulting paintsapplied by spraying to steel panels and stoved for 30 minutes at 165 C.In both cases, the hardness and the observed corrosion .resistance ofthe coated panels were superior to similar panels obtained by applying-EXAMPLE 2 1,368 parts of diphenylol propane were dissolved with warmingin 1,368 parts of butanol; to the clear solution was added a solution of225 parts of glycine in 486 parts of 37% aqueous formaldehyde. Themixture was heated at about 95 C for 1% hours when 95.5% of theformaldehyde had reacted.

To the resulting product was further added 1,094 parts of diethylaminefollowed by 905 parts of a 40% solution of formaldehyde in butanol. Thereaction mixture was kept at 94 C for 2 hours 50 minutes when 98.8% ofthe formaldehyde had reacted. Y

The final phenolic product was readily dispersed in water to give adispersion of pH 10, and was completely soluble in dilute aqueous acid.

The final phenolic product dispersed in water was mixed with thefollowing conventional water dispersible electrophoretic film-formingprimers, pigmented with red iron oxide in a pigment to binder volumeratio of 1:19, in a solids ratio phenolic product to film-forming primerof 20 to by weight;

a. maleinised linseed oil, in .which linseed oil had been reacted withmaleic anhydride in a molar ratio of l to 2 and neutralized withdiethanolamine so that the pH of the mixture was 7.8,

b. a trimellitic alkyd prepared from 2.21 parts trimellitic anhydride,1.91 parts trimethylol ethane, 1.8 parts benzyl alcohol, 1 partglycerine, 3 parts soya bean oil fatty acids and 0.45 parts benzoicacid, and neutralized with triethylamine so that the pH of the mixturewas 7.8-8,

c. an epoxy ester prepared by reacting an epoxy resin (derived fromdiphenylol propane and epichlorhydrin and of molecular weight 1,400)with dehydrated castor oil fatty acid and maleinised linseed oil fattyacid to give an acid value of mg. KOH/gm, and neutralized withdiethanolamine so that the mixture had a pH-7.8.

These composite paints and otherwise identical paints but which whichdid not contain the phenolic product were electro-deposited ontopretreated panels to give a film thickness of 0.8 thou., stoved at 165 Cand subjected to the ASTM salt spray test for 250 hours. In each casethe panels obtained from the paints containing the phenolic productshowed improved performance over the otherwise identical paints fromwhich the phenolic product had been omitted.

EXAMPLE 3 lOO parts of diphenylol propane were dissolved in a mixture of152 parts morpholine and 52 parts of butyl cellosolve. To this solution131 parts of a 40 part solution of formaldehyde in butanol were addedand reaction continued at 90 C until all the formaldehyde had reacted.

The phenolic product was soluble in alcoholic solvents and in diluteaqueous acids. When employed in paint primers similar to those ofExample 1 spray coated steel panels showed improved resistance tocorrosion over primers which did not contain the phenolic product.

lclaim:

1. An aqueous alkaline coating composition which comprises a simpleadmixture of (a) an acidic film-forming material containing at least twocarboxyl groups per molecule and (b) a phenolic material containing oneor two phenolic residues and at least two groups CH -NR,R per moleculesubstituted in positions selected from the group consisting of ortho andpara to at least one phenolic hydroxy group wherein R and R are eachselected from the class consisting of alkyl and substituted alkyl groupshaving one to 18 carbon atoms each, said film-forming material beingcross-linkable by said phenolic material upon heating.

2. A coating composition according to claim 1 wherein the acidicfilm-forming material contains a maleinized drying oil fatty acid ester.

3. A coating composition according to claim 1 wherein the acidicfilm-forming material is an addition copolymer wherein one polymerizedcomonomer contains a carboxyl group.

4. An aqueous alkaline coating composition which comprises a simpleadmixture of (a) an acidic film-forming material containing at least twofree carboxyl groups per molecule and which is an alkyd resin and (b) aphenolic material containing one or two phenolic residues and at leasttwo groups CH 'NR,R, per molecule substituted in positions selected fromthe group consisting of ortho and para to at least one phenolic hydroxygroup wherein R and R are each selected from the class consisting ofalkyl and substituted alkyl groups having one to 18 carbon atoms each,said film-forming material being crosslinkable by said phenolic materialupon heating.

5. A coating composition according to claim 1 wherein the film-formingmaterial has an acid value greater than 30 mg. KOH/gm.

6. A coating composition according to claim 1 wherein R and R eachcontain from one to six carbon atoms.

7. A coating composition according to claim 1 wherein one of the groupsR and R contains a hydroxy substituent.

8. A coating composition according to claim 1 wherein the phenolicmaterial is 2,2'-diphenylol propane having at least two substituents CH.NR,R in positions selected from the group consisting of ortho and/parato a phenolic hydroxy group.

9. A coating composition according to claim 1 wherein there is presentfrom 0.5 to 50% by weight of the phenolic material based on the totalweight of phenol material and acidic film-forming material.

10. A coating composition as set forth in claim 1 in which said acidicfilm-forming material and said phenolic material are dispersed in anaqueous medium in the presence of a water-soluble base selected from thegroup consisting of ammonia, diethyl amine, triethylamine,diethanolamine, triethanolamine, sodium hydroxide and potassiumhydroxide.

11. A coating composition according to claim 10 wherein the ghenolicmaterial contains at least one carboxyl roup.

l A coating composition according to claim 1 wherern there is presentfrom 0.5 to 40% by weight of phenolic material based on the total weightof phenolic material and acidic film-forming material.

13. A coating composition according to claim 10 wherein there is presenta water-miscible organic liquid.

2. A coating composition according to claim 1 wherein the acidicfilm-forming material contains a maleinized drying oil fatty acid ester.3. A coating composition according to claim 1 wherein the acidicfilm-forming material is an addition copolymer wherein one polymerizedcomonomer contains a carboxyl group.
 4. An aqueous alkaline coatingcomposition which comprises a simple admixture of (a) an acidicfilm-forming material containing at least two free carboxyl groups permolecule and which is an alkyd resin and (b) a phenolic materialcontaining one or two phenolic residues and at least two groups-CH2.NR1R2 per molecule Substituted in positions selected from the groupconsisting of ortho and para to at least one phenolic hydroxy groupwherein R1 and R2 are each selected from the class consisting of alkyland substituted alkyl groups having one to 18 carbon atoms each, saidfilm-forming material being crosslinkable by said phenolic material uponheating.
 5. A coating composition according to claim 1 wherein thefilm-forming material has an acid value greater than 30 mg. KOH/gm.
 6. Acoating composition according to claim 1 wherein R1 and R2 each containfrom one to six carbon atoms.
 7. A coating composition according toclaim 1 wherein one of the groups R1 and R2 contains a hydroxysubstituent.
 8. A coating composition according to claim 1 wherein thephenolic material is 2,2''-diphenylol propane having at least twosubstituents -CH2.NR1R2 in positions selected from the group consistingof ortho and/para to a phenolic hydroxy group.
 9. A coating compositionaccording to claim 1 wherein there is present from 0.5 to 50% by weightof the phenolic material based on the total weight of phenol materialand acidic film-forming material.
 10. A coating composition as set forthin claim 1 in which said acidic film-forming material and said phenolicmaterial are dispersed in an aqueous medium in the presence of awater-soluble base selected from the group consisting of ammonia,diethyl amine, triethylamine, diethanolamine, triethanolamine, sodiumhydroxide and potassium hydroxide.
 11. A coating composition accordingto claim 10 wherein the phenolic material contains at least one carboxylgroup.
 12. A coating composition according to claim 10 wherein there ispresent from 0.5 to 40% by weight of phenolic material based on thetotal weight of phenolic material and acidic film-forming material. 13.A coating composition according to claim 10 wherein there is present awater-miscible organic liquid.